|
| 1 | +..index:: |
| 2 | +single: DependencyInjection; Service Subscribers |
| 3 | + |
| 4 | +Service Subscribers |
| 5 | +================ |
| 6 | + |
| 7 | +Symfony's Service Locators provide a powerful way of passing a subset of |
| 8 | +services from the service container to a service. Sometimes, you may want a |
| 9 | +more concrete way of defining the services contained within a service locator. |
| 10 | +By implementing ``ServiceSubscriberInterface`` you can specify the contents of |
| 11 | +the service locator from the object itself. This is useful when a set of |
| 12 | +services have the same parent class and similar dependencies. |
| 13 | + |
| 14 | +Suppose you've got a mailing system with multiple ``Updater`` classes for |
| 15 | +sending out mails on different occasions. Since every updater has the same |
| 16 | +purpose, we start with a base updater:: |
| 17 | + |
| 18 | + // src/Updates/AbstractUpdater.php |
| 19 | + namespace App\Updates; |
| 20 | + |
| 21 | + use Twig\Environment; |
| 22 | + |
| 23 | + abstract class AbstractUpdater |
| 24 | + { |
| 25 | + protected $mailer; |
| 26 | + protected $twig; |
| 27 | + |
| 28 | + public function __construct(\Swift_Mailer $mailer, Environment $twig) |
| 29 | + { |
| 30 | + $this->mailer = $mailer; |
| 31 | + $this->twig = $twig; |
| 32 | + } |
| 33 | + |
| 34 | + abstract public function update($entity); |
| 35 | + |
| 36 | + /** |
| 37 | + * Renders a view with Twig |
| 38 | + */ |
| 39 | + public function render($template, $parameters) |
| 40 | + { |
| 41 | + return $this->twig->render($template, $parameters); |
| 42 | + } |
| 43 | + |
| 44 | + /** |
| 45 | + * Sends an email with Swiftmailer |
| 46 | + */ |
| 47 | + public function send($recipient, $title, $body) |
| 48 | + { |
| 49 | + $message = new \Swift_Message(); |
| 50 | + |
| 51 | + // ... |
| 52 | + |
| 53 | + $this->mailer->send($message); |
| 54 | + } |
| 55 | + } |
| 56 | + |
| 57 | +Now that we have a base class, we can add updaters for different entities. Note |
| 58 | +that we have to inject the dependencies of ``AbstractUpdater`` to each |
| 59 | +updater.:: |
| 60 | + |
| 61 | + // src/Updates/FooUpdater.php |
| 62 | + namespace App\Updates; |
| 63 | + |
| 64 | + use Doctrine\Common\Persistence\ManagerRegistry; |
| 65 | + use Twig\Environment; |
| 66 | + |
| 67 | + class FooUpdater extends AbstractUpdater |
| 68 | + { |
| 69 | + private $doctrine; |
| 70 | + |
| 71 | + public function __construct(\Swift_Mailer $mailer, Environment $twig, ManagerRegistry $doctrine) |
| 72 | + { |
| 73 | + parent::__construct($mailer, $twig); |
| 74 | + |
| 75 | + $this->doctrine = $doctrine; |
| 76 | + } |
| 77 | + |
| 78 | + public function update($entity) |
| 79 | + { |
| 80 | + // ... |
| 81 | + |
| 82 | + $body = $this->render('Emails/foo_update.html.twig', [/* ... */]); |
| 83 | + $this->send($entity->getRecipient(), 'Foo update', $body); |
| 84 | + } |
| 85 | + } |
| 86 | + |
| 87 | + // src/Updates/BarUpdater.php |
| 88 | + namespace App\Updates; |
| 89 | + |
| 90 | + use Doctrine\Common\Persistence\ManagerRegistry; |
| 91 | + use Twig\Environment; |
| 92 | + |
| 93 | + class BarUpdater extends AbstractUpdater |
| 94 | + { |
| 95 | + private $doctrine; |
| 96 | + private $barManager; |
| 97 | + |
| 98 | + public function __construct(\Swift_Mailer $mailer, Environment $twig, ManagerRegistry $doctrine, $barManager = null) |
| 99 | + { |
| 100 | + parent::__construct($mailer, $twig); |
| 101 | + |
| 102 | + $this->doctrine = $doctrine; |
| 103 | + $this->barManager = $barManager; |
| 104 | + } |
| 105 | + |
| 106 | + public function update($entity) |
| 107 | + { |
| 108 | + // ... |
| 109 | + |
| 110 | + $body = $this->render('Emails/bar_update.html.twig', [/* ... */]); |
| 111 | + $this->send($entity->getRecipient(), 'Bar update', $body); |
| 112 | + } |
| 113 | + } |
| 114 | + |
| 115 | +If you're using the `default services.yaml configuration`_, no additional |
| 116 | +configuration is required for these services thanks to autowiring, but |
| 117 | +maintaining the list of dependencies through constructor injection will quickly |
| 118 | +become cumbersome, especially if you add a dependency in ``AbstractUpdater``. |
| 119 | + |
| 120 | +By creating a service subscriber of the base class, we can create a more |
| 121 | +practical solution for our dependencies. |
| 122 | + |
| 123 | +Defining a Service Subscriber |
| 124 | +----------------------------- |
| 125 | + |
| 126 | +First, turn ``AbstractUpdater`` into an implementation of |
| 127 | +``ServiceSubscriberInterface`` by adding the static method |
| 128 | +``getSubscribedServices`` which maintains a list of subscribed services and |
| 129 | +replacing our dependencies with a service locator.:: |
| 130 | + |
| 131 | + <code> |
| 132 | + |
| 133 | +With this newly created service subscriber, the updaters can be adapted to |
| 134 | +coincide with the service locator:: |
| 135 | + |
| 136 | + <code> |
| 137 | + |
| 138 | +Optionally, you'll need to add the ``container.service_subscriber`` tag to |
| 139 | +configure the services to be recognized as service subscribers. |
| 140 | + |
| 141 | +..configuration-block:: |
| 142 | + |
| 143 | + ..code-block::yaml |
| 144 | +
|
| 145 | +<code> |
| 146 | +
|
| 147 | + ..code-block::xml |
| 148 | +
|
| 149 | + <code> |
| 150 | +
|
| 151 | + ..code-block::php |
| 152 | +
|
| 153 | + <code> |
| 154 | +
|
| 155 | +Usage |
| 156 | +----- |
| 157 | + |
| 158 | +Subscribed services |
| 159 | +------------------- |
| 160 | + |
| 161 | +Returns an array of service types required by such instances, optionally keyed by the service names used internally. |
| 162 | + |
| 163 | +For mandatory dependencies: |
| 164 | + |
| 165 | + * array('logger' => 'Psr\Log\LoggerInterface') means the objects use the "logger" name |
| 166 | + internally to fetch a service which must implement Psr\Log\LoggerInterface. |
| 167 | + * array('Psr\Log\LoggerInterface') is a shortcut for |
| 168 | + * array('Psr\Log\LoggerInterface' => 'Psr\Log\LoggerInterface') |
| 169 | + |
| 170 | +otherwise: |
| 171 | + |
| 172 | + * array('logger' => '?Psr\Log\LoggerInterface') denotes an optional dependency |
| 173 | + * array('?Psr\Log\LoggerInterface') is a shortcut for |
| 174 | + * array('Psr\Log\LoggerInterface' => '?Psr\Log\LoggerInterface') |
| 175 | + |